The presence of an infection in a wound site is typically diagnosed based on the external appearance, such as redness, swelling, odour, and/or loss of function. However, this can lead to inaccurate and untimely diagnoses, since an infection might be present without obvious symptoms. This would commonly require removal of any dressing that might be present, which can cause further pain to the patient. Therefore, there is a need for more precise methods of detecting infections, with minimal effects to the patient. Comparison of temperature differences between infected tissue and healthy tissue shows an increase ranging from 3-4 °C, while normal skin has a temperature gradient of ±1 °C. Hence, monitoring temperature of wounds can be used to detect the presence of an infection. Nanodiamonds (NDs) containing negatively charged nitrogen-vacancy (NV-) centres are capable of monitoring changes in temperature with minimal influence by environmental factors such as pH, ion concentration or molecular interaction. This study looks at encapsulating these NDs into silk fibres for use as a wound dressing that can monitor temperature changes in the wound, without requiring the removal of the dressing. To further enhance the wound healing and anti-bacterial properties, curcumin was also incorporated into the silk fibres. Curcumin is one of the active ingredients in turmeric and is known to significantly enhance wound healing through its anti-inflammatory and antibacterial properties. This study used this curcumin-nanodiamond-silk hybrid wound dressing to investigate the healing capabilities and temperature sensing properties for use as a wound dressing.
High precision magnetometry is important for a range of applications from the monitoring of biologically generated magnetic fields (e.g. magnetoencephalography and magnetocardiography), to navigation in GPS denied environments, to the detection of gravitational waves. Diamond containing the negatively-charged nitrogen vacancy colour centre (NV-) has emerged as a powerful room-temperature sensing solution. Here we explore NV- centres as a laser medium for a new form of magnetometry: laser threshold magnetometry (LTM). LTM works by placing NV- inside an optical cavity and uses the coherent laser output as a potentially more sensitive readout channel than is possible using conventional (incoherent) optically detected magnetic resonance. Here we show progress towards LTM with diamond. We show twolaser excitation and stimulated emission in free space, and report progress towards diamond-cavity experiments. Our studies highlight the need for different NV- optimisation for laser applications, rather than those conventionally used for quantum information applications
We demonstrate in-vivo chemical sensing using silk-coated exposed-core microstructured optical fibers (ECFs). The ECF provides advantages in sensitivity due to the direct access of the fiber core to the surrounding environment with integrated measurement along the entire fiber length, rather than simply the fiber tip as is common in other probes. The silk coating provides an encapsulation of the sensor molecules, and is well known as a biocompatible material. This deployable fiber sensor is fabricated with simple splicing and coating techniques, making it practical to be used in a range of biomedical sensing applications, which we demonstrate through pH sensing in a mouse model.
This work reports nanodiamond-silk membranes as an optical platform for biosensing and cell growth applications. The hybrid structure was fabricated through electrospinning and mimics a 2D scaffold with high porosity. The negatively charged nitrogen vacancy (NV-) centres in diamond exhibits optically detected magnetic resonance (ODMR), which enables sensing of temperature variations. The NV- centre, as reported in literature, provides a shift of 74 kHz in the ODMR frequency per degree rise in temperature. For our hybrid membranes, we have however observed that the embedded NV- centre provide a greater shift of 95±5 kHz/K in the ODMR frequency. This higher shift in the frequency will result in improved temperature sensitivity enabling the tracking of thermal variations in the biologically relevant window of 25-50 ºC. The thermal conductivity of silk and diamond-silk hybrid will be explored to investigate this enhanced temperature sensing ability of diamond. The hybrid diamond-silk membranes are found to be hydrophilic with a contact angle of (65±2)º. The biocompatibility of the membranes is tested both in vitro in skin keratinocyte (HaCaT) cells and in vivo in a live mouse wound model. The membranes did not induce any toxicity to the cell growth and survival. Moreover, we observed resistance towards the growth and attachment of bacteria.
We demonstrate fabrication and characterizations of intrinsically magneto-sensitive fiber with potential applications as a high-efficiency remote magnetic field sensing platform. The fibre was fabricated using lead-silicate glass and the rod-intube fibre drawing technique. The thin glass rod of ~1 mm diameter was first coated with nitrogen-vacancy (NV) centreenriched diamond particles of ~1 μm diameter, and subsequently inserted into the glass outer tube. This rod-in-tube assembly was drawn down to fibre, with the diamond particles distributed at the fused interface between rod and tube. We experimentally coupled 532 nm continuous-wave laser into a 30-cm-length fibre piece from the fibre endface, and examined the photoluminescence (PL) properties of the fibre from both the side of the fibre and the output end of the fibre. PL mapping results showed that the glass-embedded NV emitters showed bright and photostable fluorescence, demonstrating characteristic NV centre zero phonon line emission. Moreover, the mapping result obtained at the output end of fibre indicated that the transmitted NV fluorescence was coupled into the propagation modes of the fibre. By using optically detected magnetic resonance (ODMR) from the NV ensemble along the fibre, we demonstrate detection of local magnetic fields via longitudinal excitation and side collection. Based on the current light transmission and collection configuration, the hybrid diamond-glass optical fibre sensor demonstrated a shot noise-limited DC magnetic field sensitivity of 3.7 μT/√Hz at room temperature. Our results open the possibility of robust, field-deployable fibre optical magnetometry.
Nanodiamonds containing the Nitrogen-vacancy (NV) centre are emerging as a unique platform for nanoscale sensing in biological systems. There is particular interest in the capability of sensing subcellular changes of magnetic and electrical fields, temperature, and pressure. However, the sensitivity of such nanodiamond particles with NV centre as a probe is highly dependent on the relative location and polarisation of the NV centre to the bulk of the particle. Here we show the optical scattering from an NV centre in a nanodiamond as a function of position and orientation within the nanodiamond. The scattering fields are obtained by using the recently developed robust non-singular surface integral equation method.1, 2 Our results highlight a new pathway to nanodiamond characterisation which may be useful in teasing out the various effects of surface morphology, surface termination, and formation details, which ultimately may benefit the optimisation of diamond production for nanoscale biosensing applications.
Fluorescent nanodiamonds made from high-pressure high-temperature diamond are increasingly used in biological imaging and sensing applications. To date, only red and green fluorescent nanodiamonds are widely available, severely limiting nanodiamond-based multiplexed imaging. Here, we report on recent progress in the fabrication and characterization of fluorescent nanodiamonds with fluorescence colors from 450 nm to 900 nm. The fluorescence originates from a range of fluorescent color centers based on nitrogen, silicon, nickel and vacancy defects in the diamond lattice. The optical properties of these color centers in diamond nanoparticles are discussed in detail and the utility of nanodiamond-based multiplexed bioimaging demonstrated in experiments in-vitro.
The nitrogen-vacancy (NV) centre in diamond is a perfect candidate for quantum sensing applications applied to numerous fields of science. Past studies improved the sensitivity of diamonds containing NV centres by increasing their density or prolonging their coherence time. However, few studies discussed the effects of other defects inside the diamond crystal on the sensitivity of the NV centres. In this study, we demonstrated the implication of single substitutional nitrogen defects on the fluorescence emission, charge state stability, coherence time and sensitivity of the NV centres. We found that there is an optimal concentration of nitrogen defects that allows diamond samples to have a high-density of NV centres and high fluorescence without significantly affecting the coherence time. This results will inform the correct choice of diamond characteristics for current and future quantum sensing applications with the NV centres.
Optical fiber bundles are the backbone of modern, ultra-thin, clinical fluorescence microendoscopes. Each core in the bundle acts as a pixel, allowing image transmission from inside hard to reach spaces in the body. Each core relays light from a given location in 2D space and therefore the bundle is thought to yield only a 2D image. However, we show that these fiber bundles do in fact transmit 3D information about the scene, by way of intensity distribution within the cores.
Our key observation is that the intra-core intensity distribution depends on the angular coupling efficiency of incoming light. Normally incident light tends to couple into the fundamental mode of the core, whereas oblique light couples to higher order modes that carry most of their energy near the core/cladding interface. By leveraging this phenomenon, we are able to extract 3D information from fiber bundle-based microendoscopes in the form of a light field. We show that this light field 3D information can be visualized in many ways, from stereo images to full-parallax animations, refocusing and depth mapping. Our light field fiber bundle imaging technique is single-shot, resistant to fiber bending and does not require any physical modification to stock optical fiber bundles.
In this talk we will outline the mathematical model of our technique and present several examples of light field fluorescence imaging through bare optical fiber bundles.
Mobile phones come equipped with a vast array of actuation and sensing technologies, making them an ideal platform for point-of-care diagnostics and information gathering. Mobile phone microscopes take advantage of the small pixel size on mobile phone camera sensors for micron-scale resolution. Focusing can be achieved with built-in autofocus and image processing can be done on-board, however, the illumination is typically introduced via an external light emitting diode (LED). These external LEDs are typically externally powered, adding bulk and cost to a system that is meant to be as affordable as possible. In this work, we present a mobile phone microscope that uses the phone's integrated flash as an illumination source, eliminating the need to engineer an external illumination into the system. Our design consists of a 3D printed clip-on module containing a lens, which together with the mobile phone camera lens acts as an infinite-conjugate microscope. The clip-on module functions as a basic sample holder, and contains a series of light tunnels that redirect light from the flash through the sample for brightfield illumination. Instead of mirrors and a condenser lens, diffuse reflection from the internal light tunnel of the plastic clip-on module both reflects and scatters light into a range of illumination angles – ideal for brightfield microscopy. For low-contrast samples, darkfield imaging is achieved with ambient lighting via internal reflection within the sample microscope slide. We demonstrate imaging and video microscopy of a range of samples including plants, cell cultures and cattle semen.
The direct write of photonic elements onto substrates presents opportunities for rapid prototyping and novel sensing architectures in domains inaccessible to traditional lithography. In particular, focussed electron beam induced deposition (FEBID) of platinum is a convenient technology for such direct-write applications with the advantage of relatively controlled deposition parameters and sub-10 nm resolution. One issue for FEBID of platinum is that the precursor gas contains a relatively high carbon content, which in turn leads to carbonaceous deposits in the final structure. Here we explore the creation of plasmonic nanoantennae using FEBID platinum. We compare as-deposited and annealed antenna with heights of 40 nm and 56 nm, showing the effect of annealing on the carbon concentration and hence the optical properties. These results are compared with modelling using Mie scattering theory. Our results show that FEBID platinum is a useful material for the direct-write of plasmonic nanoantenna.
We report the generation of sub-surface nanouidic channels from single crystal diamond. To make the channels, we used a combination of ion-beam induced damage and annealing to create a buried, etchable graphitic layer in the diamond. Either laser or focussed ion-beam milling was then used to connect to that layer, and subsequent electro-chemical etching used to remove the graphitic material. The channels had dimensions 100-200 nm thick, 100 μm wide and 300 μm long, which have a total volume around 3 pL; and were around 3 μm below the diamond surface.
The porous properties of self-assembled waveguides made up of nanoparticles are characterised. Atomic force microscopy (AFM) reveals predominantly hcp or fcc packing suggesting a remarkably well ordered and distributed porous structure. N2 adsorption studies estimate a surface area SA ~ 101 m2/g, a total interstitial volume Vi ~ 1.7 mL/g and a pore size distribution of r ~ (2 - 6) nm. This distribution is in excellent agreement with the idealised values for identically sized particles obtained for the octahedral and tetrahedral pores of the hcp and fcc lattices, estimated to lie within and rtet ~ (2.2 – 3.3) nm and roct ~ (4.2 – 6.2) nm for particles varying in size over 20 to 30 nm. Optical transmission based percolation studies reveal rapid penetration of Rhodamine dye (< 5 s) with very little percolation of larger molecules such as ZnTPP observed under similar loading conditions. In the latter case, laser ablation was used to determine the transport of hydrated Zn2+ to be D ~ 3 x 10-4 nm2s-1. By comparison, ZnTPP was not able to percolate into the wire over the time of exposure, t = 10 mins, effectively demonstrating the self-assembled structure acting as a molecular sieve. We discuss the potential of such structures more broadly and conclude that the controllable distribution of such nano-chambers offers the possibility of amplifying, or up-scaling, an otherwise local interaction or nanoreactions to make detection and diagnostics much simpler; it also opens up a new approach to material engineering making new composites with periodic nanoscale variability. These and other unique aspects of these structures are embodied in an overall concept of lab-in-wire, or similar self-assembled structures, extending our previous concept of lab-in-fibre from the micro domain into the nano domain.
Recent advances in the production of high-purity synthetic diamonds have made diamond an accessible host material for
applications in present and future optoelectronic and photonic devices. We have developed a scalable process for
fabricating photonic devices in diamond using reactive ion etching (RIE) and photolithography as well as using ion
implantation to provide vertical confinement. Applying this we have demonstrated a few-moded waveguide with a large
cross section for easier coupling to optical fibre. We present our work towards in-plane coupling to diamond waveguides
and consequently characterisation of these waveguides. We also examine the application of diamond waveguides to other
photonic applications for achieving light confinement in a subwavelength cavity site using a slot-waveguide design. Such
cavities may be used to enhance photon-emission properties of a built-in diamond colour centre and to achieve strong
light-matter interactions on the single-quantum level necessary for quantum information technology. Using single
cavities as building block, we also show that these structures can be suitably coupled to form one-dimensional coupled-resonator
Diamond has a range of extraordinary properties and the recent ability to produce high quality synthetic diamond has
paved the way for the fabrication of practical diamond devices. This paper details the recent progress in the fabrication of
waveguide structures in diamond which are desirable as the basis for quantum key distribution (QKD), quantum computing and high-power, high speed microwave chips. The diamond ridge waveguide structures are produced by photolithography and reactive ion etching (RIE) with some additional processing with a focused ion beam (FIB). The processes currently used are discussed along with experimental results. Future fabrication goals and potential methods for achieving these goals are also presented.
Resonant nanostructured metallic devices have attracted considerable recent attention through phenomena such as
extraordinary transmission and their potential application as sensing elements, metamaterials and for enhancing
nonlinear optical effects. Here we report on the investigation of the geometry and material properties on the performance
of periodic and random arrays of coaxial apertures in thin metallic films. Such apertures in perfect conductors have been
shown to resonate at a wavelength governed by the geometry of the apertures leading to enhanced transmission. This
resonant wavelength is dictated by the cutoff wavelength of the fundamental mode propagating in the corresponding
coaxial waveguide and, as a consequence, is largely independent of whether the apertures are isolated or in random or
periodic arrangements. In the case of periodic samples, however, these resonances can coherently couple to surface
waves to produce an analogue of the enhanced optical transmission seen in arrays of circular and other apertures. We
have previously shown that as the width of the rings decreases, there are substantial red-shifts in the resonant wavelength
from that predicted for perfect conductivity when the optical properties of the metal are considered. Here we report on
recent developments in fabrication, design and modelling of metallic resonant structures and their near- and far-field
optical characterisation. In particular, we consider the relationship between random and regular arrangements of
The near and far-field transmission characteristics of nanoscale annular array metamaterials fabricated using ion beam
lithography are investigated both computationally and experimentally. Experimental results in the far-field regime
demonstrate high transmission efficiencies in the near infra-red region of the electromagnetic spectrum for these devices,
in excellent qualitative agreement with a previously developed numerical model. The diffractive near-field behavior of
such structures is discussed, with a particular emphasis on the implications associated with verifying such predictions
We describe how a quantum non-demolition device based on electromagnetically-induced transparency in solidstate atom-like systems could be realized. Such a resource, requiring only weak optical nonlinearities, could potentially enable photonic quantum information processing (QIP) that is much more efficient than QIP based on linear optics alone. As an example, we show how a parity gate could be constructed. A particularly interesting physical system for constructing devices is the nitrogen-vacancy defect in diamond, but the excited-state structure for this system is unclear in the existing literature. We include some of our latest spectroscopic results that indicate that the optical transitions are generally not spin-preserving, even at zero magnetic field, which allows the realization of a Λ-type system.